Centrifuge construction



' o. w. JOHNSON CENTRIFUGE CONSTRUCTION Nov. 3, 1959 Filed Dec. 20, 1955 3 Sheets-Sheet 1 INVENTOR. Qrcar V14 Johnson ATTORNEVJ Nov. 3, 1959 o. w. JOHNSON CENTRIFUGE CONSTRUCTION 3 Sheets-Sheet 2 Filgd Dec. 20, 1955 N v 5 Q & Q N a Q Q Q i1 a w A Harm; :XNN w x NM 1 E m r UHnH i zzu a iu;

ATTORNEY! Nov. 3, 1959 o. w. JOHNSON CENTRIFUGE CONSTRUCTION Filed Dec. 20, 1955 Sheets-Sheet 3 INVENTOR. Oscar l/kJa/vnson HTTORA/E V5 United States -Patent.

CENTRIFUGE CONSTRUCTION Oscar W. Johnson Houston Tex., assignor, by mesne assignments, to Dorr-oliviar Incorporated, Stamford, Conn., a corporation of Delaware Application December 20', 1955, Serial No. 554,173 3 Claims. (Cl. 2332)' This invention relates generally to centrifuge machines of the type adapted'for the continuous separation and discharge of solid components from a feed material.

Commercial centrifuges are available whicharesupplied with feed material continuously, as distinguished from batch operation, and which effect continuous centrifugal separation with discharge of an underflow containing heavier solid components. Such continuous machines are disclosed for example in Patents 'No. 2,525,629, 2,559,453, 2,616,620 and 2,625,321. The machines disclosed in said patents utilize so-called return circuits, by means of which a large part of the centrifugally separated underflow is continuously returned into the centrifuge rotor, to thereby increase the amount of material of underflow consistency continuously discharging through the underflow nozzles. When employed in certain commercial processing operations, such machines may be subject to troublesome clogging of the underflow nozzles. Clogging reduces operating capacity, and makes it necessary to shut the machine down for servicing. Troublesome clogging of the underflow nozzles may be experienced even though screening or sizing methods are used on the feed material, to preventsupplying solid particles of a size apt to cause clogging. With certain types of feeds the clogging may be caused by a build up of solid material within the centrifuge chamber, with occasional sloughing off of built up fragments of a size sufficient to cause clogging. In other instances the clogging may be experienced immediately after the machine is placed in operation following a shut-down period, and may be due to a build up of deposits occurring during shut-down, which slough :ofi' when the machine is started in operation.

In general it is the object of the present invention to provide an improved centrifuge which is constructed to avoid the type of clogging referred to above.

Another object of the inventionis to provide amachine of the above character having screening means serving to prevent clogging of the underflow discharge nozzles.

An additional object of the invention is to provide a machine of the above character in which the screen can be easily removed for servicing or replacement.

Additional objects and features of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing. 1

Referring to the drawing:

Figure l is a side elevational view in one-half section illustrating a centrifuge machine incorporating the present invention.

Figure 2 is a cross-sectional detail taken along lines 2-2 of Figure 1.

Figure 3 is an enlarged cross-sectional detail showing the screen and the manner in which it is mounted.

Figure 4 is an enlarged cross-sectional detail likewis taken along line 22 of Figure 1,

2,911,139 PatentedNov. 3, 1959 ice Figure 5 is an enlarged cross-sectional detail like Figure3, but showing another embodiment.

Figure 6 is an enlarged cross-sectional detail like Figure 3, but showing, another embodiment.

Figure 7 is an enlarged cross-sectional detail like Figure 3, but showing another embodiment.

The centrifuge as illustrated in the drawing consists of a rotor 10, carried by the vertical shaft 11. The housing 12 encloses the rotor and is provided with means for collecting the underfiow and overflow materials, as Will be presently explained. The upper and lower main sections 10a and 10b of the rotor are secured together by suitable means such as the clamping ring 13;. The outer peripheral portion 14 of the rotor carries a plurality of underflow discharge nozzles '16. Each of these nozzles may be constructed in a manner disclosed in Patent 2,695,748. Thus as shown in Figure 4 each nozzle can consist of an annular body 17 fitted within an accommodating bore' 18, and sealed with respect to the rotorby suitable means such as the resilient O-ring 19. The body 17 may be provided with the liner 21 of suitable wear-resisting material, which is sealed with. respect to .the body by suitable means such as the resilient O-ring 22. The nozzle discharge orifice 23 is directed backwardly with respect to the direction of rotation. The periphery of the rotor is cut away at 24 to accommodate the discharging material. The number of underflow nozzles may vary in different instances, depending upon the size of the machine, the capacity of operation, and the type of material upon which separation is being made.

Underflow material discharging from the nozzles 16 is collected in the housing volute 26. This volute is connected with external piping whereby a large amount of the underfiow material is continuously returned back into the lower impeller portion 27 of the rotor, through the upwardly directed velocity control device 28. Such an arrangement is disclosed for example in Patent 2,616,620. The impeller portion 27 of the rotor serves to deliver the underflow material outwardly through the passages 29, and through the annular orifice 31 into the centrifuge chamber 32.

The centrifuge chamber is provided with spaced separating disks 33, and with suitable provision for the discharge of a centrifugally separated overflow, such as the overflow discharge lip 34'. The overflow is collected in the volute 36, for removal.

The underflow discharge nozzles 16 receive material from regions 37 which are located outwardly with respect to the main separating chamber. In the embodiment illustrated in Figures 1 and 2, the regions 3-7 are hopper shaped, :and are separated and contoured by the socalled hopper blocks 38. These hopper-blocks can be made of suitable material, such as fabric reinforced molded plastic, and are each held in place by suitable means such as a screw 39. The annular rotor space 41, which accommodates the blocks 38, and which provides the hopepr shaped regions 37' between the blocks, may be formed as an outward extension of the main centrifuge chamber. 1

As shown particularly in Figures 3 and 4, I provide a sizing screen 42 which is mounted directly within the rotor. This screen is in the form of a continuous annu lar band, and can be formed of suitable woven wire having sufficient strength for the speeds of rotation employed, and having sufficient hardness to resist the abrasion to which it may be subjected. In most in stances it is most satisfactory to use one of the so-called stainless steels. Any splicing of the Wires should be by a technique which does not disturb the balance of the troublesome clogging of the underfiow nozzles.

than the diameter of the nozzle orifices.

As shown in Figures 2-4 the screen 42 is supported upon the inner ends of the hopper blocks 38. The upper edge 43 can be seated upon the surface 44of the rotor, and similarly the lower edge 46 may be seated upon the surface 47. Assuming that the screen is of proper size, and that it has a fair degree of spring, it will remain in its desired position without further securing means. It will be evident that when the two bowl parts a and 10b are separated, the screen can be distorted within its elastic limit and removed.

The centrifuge construction described above eliminaiefi material being delivered to the underflow nozzles must pass through the screen 42, and therefore any oversized material which may be present is removed at this point. This applies not only to oversized material which may accidentally find its way into the feed, but also deposits building up within the centrifuge rotor, which may slough off to cause clogging.

A feature of the invention is the fact that the screen 42 is located in a region of considerable turbulence, which tends to provide a form of self-cleaning action. Turbulence is caused by underflow material being returned through passage 29, and through the annular orifice 31 into the region adjacent the inner face of the screen 42. Therefore due tosuch turbulence solid material being retained upon the inner face of screen 42 is subjected continuously to attrition and crushing forces, tending to reduce the fragments to smaller particles which passthrough the screen and the discharge nozzles. This self-cleaning action may materially extend the periods of operation of the machine between periods of shutdown for cleaning.

The machine mentioned in the foregoing description employs return passages 29 which are formed between intervening vanes on the rotor member 48. The invention can also be used on a machine of the type utilizing tubes for returning underflow material, as illustrated in Figure 5. Thus in this instance circumferentially spaced tubes 49 are provided for discharging under-flow material back into the rotor, and the outer ends of these tubes are arranged to terminate short of the screen 42.

The machine in this instance is shown provided with hopper blocks 38 the same as in Figures 1-4.

The embodiment shown in Figure 6 includes a rotor 51 having an annular space 52 of limited radial extent that communicates with the separating chamber 53 and delivers underflow to the nozzles 54. Suflicient recessing is provided at 55 and 56 to seat the upper and lower edges of the annular screen 57. The return circuit for underflow material includes the passages 58 that deliver the returned underflow into a region directly adjacent the inner side of the screen.

In the embodiment of Figure 7 the rotor 61 is pro- 2,911,139 r e g vided with recesses 62 and 63 to seat the upper and lower edges of the screen 64. The return circuit in this instance includes the radially extending tubes 66 that deliver returned underflow material into circumferentially spaced regions adjacent the inner side of the screen. Underflow material passing through the screen is delivered to the nozzles 67.

It will be evident from the foregoing that my machine makes it possible to operate over long periods of time on a wide variety of feed materials without clogging. The machine may continue to operate until the amount of solid material deposited upon screen 42 is such as to materially reduce the capacity of the machine. When this occurs the rotor is dismantled and the screen cleaned.

I claim:

1. In a centrifuge of the continuous type, a rotor having means for supplying a feed material to the same and also having peripheral nozzles for the continuous discharge of an underfiow and means for discharging a lighter centrifugally separated overflow, the rotor having a main separating chamber adapted to receive the feed material, said peripheral underflow nozzles communicating with regions within the rotor that generally surround the main separating chamber, said regions being separated by hopper forming blocks, and an annular screen seated within the rotor and interposed between said regions and the main separating chamber, the inner ends of said blocks serving to support said screen.

2. In a centrifuge of the continuous type, a rotor having means for supplying a feed to the same and also having peripheral nozzles for the discharge of a heavier centrifugally separated underflow and means for the discharge of a centrifugally separated overflow, said nozzles communicating with regions within the rotor that generally surround the main separating chamber of the rotor, a screen interposed between the main separating chamber and said regions, said screen being in the form of an endlessannular band, and means for continuously returning a substantial part of the discharged underflow back into the separating chamber, said means serving to discharge returned underflow material into the outer portion of the main separating chamber and in a region adjacent the inner side of said screen, whereby solid material on the screen is subjected to distintegrating forces.

3. A centrifuge as in claim 2 in which said regions are separated .by hopper forming blocks secured to the rotor, and in which the inner ends of said blocks serve to support said screen.

References Cited in the file of this patent UNITED STATES PATENTS 2,724,549 Brown Nov. 22, 1955 FOREIGN PATENTS 408,926 Great Britain July 13, 1932 

